Investigations of human exposure to environmental contaminants were funded by this research budget in FY2019 as follows: 1) Anniston community health survey (ACHS-II): Follow-up study and dioxin analyses. This is a major cross-sectional epidemiology investigation in residents of Anniston, Alabama exposed over time to PCBs and other contaminants from a local chemical production facility. A previous study conducted by the Agency for Toxic Substances and Disease Registry (ATSDR) of the Centers for Disease Control (CDC) found elevated blood levels of PCBs in the population associated with a high incidence of hypertension and diabetes. The current study partners with ATSDR to assess current blood concentrations of non-dioxin-like and dioxin-like PCBs, other dioxin-like chemicals, persistent pesticides, and heavy metals in some participants of the earlier study. The results will be used for health and risk management for the exposed individuals. The recruitment and sampling phases of this study are concluded. Blood was collected from 359 of 777 subjects from the original study. Laboratory analysis of these samples is underway. Preliminary results from some participants indicate a decrease over time in serum levels of many PCB congeners, especially those of lowest chlorination. New research is underway to assess the degree of DNA methylation (biomarker of chemical exposure) in these subjects. 2) Toxic organic chemicals and heavy metals in blood and urine of electronic waste recycling workers and the general population in rural Vietnam. This collaborative study with Vietnamese researchers and others compares concentrations of heavy metals, PCBs, dioxins, and other POPs in e-waste recyclers and a control cohort. Sample analysis conducted in FY2015 detected elevated levels of some organic pollutants in the workers and of some heavy metals in subjects from both cohorts. Results from these studies were reported at scientific meetings in FY2017 and a manuscript describing the Biomonitoring of Organics and Metals in Vietnamese Female Electronic Waste Recyclers was published in FY2018. A final manuscript describing Biomonitoring and Health Effects of Organics, Metals, Dioxins, Pesticides, and Other Chemicals of Interest in E-Waste Recycling Women Located in Rural Northern Vietnam will be submitted for publication in late FY2019 or early FY2020. 3) Bisphenol A (BPA) pharmacokinetics: Controlled exposure study. This study is being conducted in collaboration with NIEHS and NTP researchers. The results for an oral exposure to 14 subjects were published in FY2015. Dermal application studies are in progress. These data will be used for further understanding of the fate of this potential endocrine disruptor in humans. Studies of the fate and toxicity of several brominated flame retardants (BFRs) and other halogenated chemicals of interest were conducted in the PI's research laboratory in FY2019 as follows: 1) Studies of the major flame retardant tetrabromobisphenol A (TBBPA). Results from the collaborative prenatal & perinatal were reported at scientific meetings in FY2017 and a manuscript describing the disposition of TBBPA in pregnant and nursing rats was published in FY2019. 2) Chronic exposure to tetrabromobisphenol A potentially alters circadian rhythm in rats Using tissues from previous studies of Wistar Han rats treated with TBBPA (250 mg/kg/d for 5 days), RNA-Seq analysis of liver and uterus from the TBBPA and vehicle treated rats also indicated a possible effect on expression of the genes controlling circadian rhythm. After accounting for differences in time of euthanasia, results showed a possible shift of the gene expression in the uterus but not the liver of the animals treated with TBBPA. These changes are expected to alter the estrus cycle and represent a possible pathway for perturbation of estrogen levels in the uterus, as well as affecting expression of numerous other genes which are reliant on circadian signals to regulate expression. Preliminary findings from these studies were presented at a scientific meeting in FY2019 and a manuscript describing these data will be submitted for publication in early FY2020. 3) Studies of the major flame retardant 2,4,6-tribromophenol (TBP). Final results of these studies were reported at scientific meetings in FY2019 and a manuscript describing the disposition of TBP in rodents was published in FY2019. The disposition of TBP in pregnant and nursing rats is under investigation, with preliminary findings presented at a scientific meeting in FY2019 and a manuscript describing these data will be submitted for publication in early FY2020. 4) Studies of dermal disposition of Tetrabromobisphenol A bis(2,3-dibromopropyl ether) (TBBPA-BDBPE) Little toxicity data are available for TBBPA's replacement alternative TBBPA-BDBPE, but its additive usage poses a higher risk of migration into environmental matrices. These studies indicate that all three chemicals are likely to be dermally bioavailable and dermal contact with these agents should be considered an important route of exposure. Final results of these studies were reported at scientific meetings in FY2018 and a manuscript describing the dermal disposition of TBBPA-BDBPE was published in FY2019. 5) Studies of efflux transporter activity and function in barrier tissues following xenobiotic exposure to TBBPA. Results of these studies were reported at scientific meetings in FY2019 and were published in FY2019. 6) Studies of efflux transporter activity and function in barrier tissues following xenobiotic exposure to TBP. Results of these studies were reported at scientific meetings in FY2019 and were submitted for publication in FY2019. 7) Studies of efflux transporter activity and function in barrier tissues following xenobiotic exposure to GenX. Results of these studies were reported at scientific meetings in FY2019 and will be submitted for publication in late FY2019. 8) Screening studies of efflux transporter activity and function in barrier tissues following xenobiotic exposure using medium- to high-throughput screening. An ImageXpress Micro Confocal (IXM) has been employed to screen multiple environmental contaminants for modulation of P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) transport activity in rat brain microvessels. This assay utilizes 96-well plates containing freshly isolated ex vivo male rat brain capillaries are imaged using the IXM and analyzed using MetaXpress software to identify capillaries and quantify the steady-state luminal accumulation of a transporter-specific fluorescent substrate. Treatment with specific inhibitors, PSC833 (P-gp) and KS176 (BCRP), led to decreases in P-gp and BCRP transport activity, supporting assay feasibility. The IXM offers a new avenue for medium-throughput screening of chemicals that may impact the integrity and regulation of the BBB. Once optimized, this assay will have broad applications across basic science and pharmaceutical development. Preliminary of these studies were reported at scientific meetings in FY2019 and will be submitted for publication in early FY2020. In addition to the studies previously described, the PI of this laboratory contributed time and effort as a co-contributor to other works associated with the research goals of this project. In FY2019, this research project also funded development of PBPK models in rodents for extrapolation to human risk assessment efforts.